1. Field of the Invention
The present invention related to a crane that repeats traveling and working and its rotating superstructure.
2. Description of Related Art
There is a rotating superstructure (revolving superstructure) known in the prior art, on which a power unit that includes an engine, a radiator and the like and a unit for raising and lowering a boom that includes a winch, an arm and the like are mounted and a counterweight is attached. In general, when a rotating superstructure is transported, the counterweight is removed from the rotating superstructure so as to reduce the transportation weight (for instance, refer to Japanese Laid Open Patent Publication No. 2007-230747).